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Electronic Control Transmission (ECT)

Electronic Control Transmission (ECT)The Electronic Control Transmission is an automatic Transmission which uses modern Electronic Control technologies to Control the Transmission . The Transmission itself, except for the valve body and speed sensor, is virtually the same as a full hydraulically controlled Transmission , but it also consists of Electronic parts, sensors, an Electronic Control unit and actuators. The Electronic sensors monitor the speed of the vehicle, gear position selection and throttle opening, sending this information to the ECU. The ECU then controls the operation of the clutches and brakes based on this data and controls the timing of shift points and torque converter lock-up. Driving Pattern Select SwitchThe pattern select switch is controlled by the driver to select the desired driving mode, either "Normal" or "Power." Based on the position of the switch, the ECT ECU selects the shift pattern and lock-up accordingly. The upshift in the power mode will occur later, at a higher speed depending on the throttle opening.

L1, L2, L3 and IDL to make and break the circuit with contact E (ground). The grid which the contact points slide across is laid out in such a way as to provide signals to the ECT ECU depicted in the chart below. The voltage signals provided to the ECT ECU indicate throttle position just as they did in the indirect type of sensor.

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Transcription of Electronic Control Transmission (ECT)

1 Electronic Control Transmission (ECT)The Electronic Control Transmission is an automatic Transmission which uses modern Electronic Control technologies to Control the Transmission . The Transmission itself, except for the valve body and speed sensor, is virtually the same as a full hydraulically controlled Transmission , but it also consists of Electronic parts, sensors, an Electronic Control unit and actuators. The Electronic sensors monitor the speed of the vehicle, gear position selection and throttle opening, sending this information to the ECU. The ECU then controls the operation of the clutches and brakes based on this data and controls the timing of shift points and torque converter lock-up. Driving Pattern Select SwitchThe pattern select switch is controlled by the driver to select the desired driving mode, either "Normal" or "Power." Based on the position of the switch, the ECT ECU selects the shift pattern and lock-up accordingly. The upshift in the power mode will occur later, at a higher speed depending on the throttle opening.

2 For example, an upshift to third gear at 50% throttle will occur at about 37 mph in normal mode and about 47 mph in power mode. TOYOTA Electronic Control Transmission Page 1 Toyota Motor Sales, , Inc. All Rights ECU has a "PWR" terminal but does not have a "Normal" terminal. When "Power" is selected, 12 volts are applied to the "PWR" terminal of the ECU and the power light illuminates. When "Normal" is selected, the voltage at "PWR" is 0 volts. When the ECU senses 0 volts at the terminal, it recognizes that "Normal" has been selected. Beginning with the 1990 MR2 and Celica and the 1991 Previa, the pattern select switch was discontinued. In the Celica and Previa systems, several shift patterns are stored in the ECU memory. Utilizing sensory inputs, the ECU selects the appropriate shift pattern and operates the shift solenoids accordingly.

3 The MR2 and 1993 Corolla have only one shift pattern stored in the ECU memory. Neutral Start SwitchThe ECT ECU receives information on the gear range into which the Transmission has been shifted from the shift position sensor, located in the neutral start switch, and determines the appropriate shift pattern. The neutral start switch is actuated by the manual valve shaft in response to gear selector movement. The ECT ECU only monitors positions "T' and "L." If either of these terminals provides a 12-volt signal to the ECU, it determines that the Transmission is in neutral, second gear or first gear. If the ECU does not receive a 12-volt signal at terminals "T' or "1," the ECU determines that the Transmission is in the "D" range. Some neutral start switches have contacts for all gear ranges. Each contact is attached to the gear position indicator lights if the vehicle is so equipped. TOYOTA Electronic Control Transmission Page 2 Toyota Motor Sales, , Inc.

4 All Rights addition to sensing gear positions, the neutral switch prevents the starter from cranking the engine unless it is in the park or neutral position. In the park and neutral position, continuity is established between terminals "B" and "NB" of the neutral start switch illustrated below. Throttle Position SensorThis sensor is mounted on the throttle body and electronically senses how far the throttle is open and then sends this data to the ECU. The throttle position sensor takes the place of throttle pressure in a fully hydraulic Control Transmission . By relaying the throttle position, it gives the ECU an indication of engine load to Control the shifting and lock-up timing of the Transmission . There are two types of throttle sensors associated with ECT transmissions . The type is related to how they connect to the ECT ECU. The first is the indirect type because it is connected directly to the engine ECU, and the engine ECU then relays throttle position information to the ECT ECU.

5 The second type is the direct type which is connected directly to the ECT ECU. TOYOTA Electronic Control Transmission Page 3 Toyota Motor Sales, , Inc. All Rights TypeThis throttle position sensor converts the throttle valve opening angle into voltage signals. It has four terminals: VC, VTA, IDL and E. A constant 5 volts is applied to terminal VC from the engine ECU. As the contact point slides along the resistor with throttle opening, voltage is applied to the VTA terminal. This voltage increases linearly from 0 volts at closed throttle to 5 volts at wide-open throttle. The engine ECU converts the VTA voltage into one of eight different throttle opening angle signals to inform the ECT ECU of the throttle opening. These signals consist of various combinations of high and low voltages at ECT ECU terminals as shown in the chart below. The shaded areas of the chart represent low voltage (about 0 volts).

6 The white areas represent high voltage (L1, L2, U: about 5 volts; IDL: about 12 volts). TOYOTA Electronic Control Transmission Page 4 Toyota Motor Sales, , Inc. All Rights the throttle valve is completely closed, the contact points for the IDL signal connect the IDL and E terminals, sending an IDL signal to the ECT ECU to inform it that the throttle is fully closed. As the ECT ECU receives the L1, L2 and D signals, it provides an output voltage from 1 to 8 volts at the TT or ECT terminal of the diagnostic check connector. The voltage signal varies depending on the throttle opening angle and informs the technician whether or not the throttle opening signal is being input properly. Direct TypeWith this type of throttle sensor, signals are input directly to the ECT ECU from the throttle position sensor. Three movable contact points rotate with the throttle valve, causing contacts L1, L2, L3 and IDL to make and break the circuit with contact E (ground).

7 The grid which the contact points slide across is laid out in such a way as to provide signals to the ECT ECU depicted in the chart below. The voltage signals provided to the ECT ECU indicate throttle position just as they did in the indirect type of sensor. If the idle contact or its circuit on either throttle sensor malfunctions, certain symptoms occur. If it is shorted to ground, lock-up of the torque converter will not occur. If the circuit is open, neutral to drive squat Control does not occur and a harsh engagement may be the result. If the L1, L2, L3 signals are abnormal, shift timing will be incorrect. TOYOTA Electronic Control Transmission Page 5 Toyota Motor Sales, , Inc. All Rights Temperature SensorThe water temperature sensor monitors engine coolant temperature and is typically located near the cylinder head water outlet.

8 A thermistor is mounted within the temperature sensor, and its resistance value decreases as the temperature increases. Therefore, when the engine temperature is low, resistance will be high. When the engine coolant is below a predetermined temperature, the engine performance and the vehicle's drivability would suffer if the Transmission were shifted into overdrive or the converter clutch were locked-up. The engine ECU monitors coolant temperature and sends a signal to terminal OD1 of the ECT ECU. The ECU prevents the Transmission from upshifting into overdrive and lock-up until the coolant has reached a predetermined temperature. This temperature will vary from 122'F to 162 F depending on the Transmission and vehicle model. For specific temperatures, refer to the ECT Diagnostic Information chart in the appendix of this book. Some models, depending on the model year, cancel upshifts to third gear at lower temperatures. This information is found in the appendix and is indicated in the heading of the OD Cancel Temp column of the ECT Diagnostic Information chart by listing in parenthesis the temperature for restricting third gear.

9 TOYOTA Electronic Control Transmission Page 6 Toyota Motor Sales, , Inc. All Rights SensorsTo ensure that the ECT ECU is kept informed of the correct vehicle speed at all times, vehicle speed signals are input into it by two speed sensors. For further accuracy, the ECT ECU constantly compares these two signals to see whether they are the same. The speed sensor is used in place of governor pressure in the conventional hydraulically controlled Transmission . Main Speed Sensor (No. 2 Speed Sensor)The main speed sensor is located in the Transmission housing. A rotor with built-in magnet is mounted on the drive pinion shaft or output shaft. Every time the shaft makes one complete revolution, the magnet activates the reed switch, causing it to generate a signal. This signal is sent to the ECU, which uses it in controlling the shift point and the operation of the lock-up clutch.

10 This sensor outputs one pulse for every one revolution of the output shaft. Beginning with the 1993 Corolla A245E, the No. 2 speed sensor has been discontinued and only the No. 1 speed sensor is monitored for shift timing. TOYOTA Electronic Control Transmission Page 7 Toyota Motor Sales, , Inc. All Rights Up Speed Sensor ( Speed Sensor)The back-up speed sensor is built into the combination meter assembly and is operated by the speedometer cable. The sensor consists of an electrical reed switch and a multiple pole permanent magnet assembly. As the speedometer cable turns, the permanent magnet rotates past the reed switch. The magnetic flux lines between the poles of the magnet cause the contacts to open and close as they pass. The sensor outputs four pulses for every one revolution of the speedometer cable. The sensor can also be a photocoupler type which uses a photo transistor and light-emitting diode (LED).


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